1. Field of the Invention
The present invention relates to a method for driving a light-emitting device in which a transistor is provided in each pixel.
2. Description of the Related Art
In an active matrix display device using a light-emitting element, in general, at least a light-emitting element, a transistor (a switching transistor) which controls input of a video signal to a pixel, and a transistor (a driving transistor) which controls a value of current supplied to the light-emitting element are provided in each pixel. In a light-emitting device having the above-described structure, drain current of the driving transistor is supplied to the light-emitting element; thus, when a variation in the threshold voltages of the driving transistors occurs among pixels, the luminances of light-emitting elements vary correspondingly.
Further, in the case where an n-channel transistor having higher mobility than a p-channel transistor is used as a driving transistor, a source of the driving transistor is connected to an anode of a light-emitting element. In that case, when the voltage between the anode and the cathode of the light-emitting element is increased owing to deterioration of an electroluminescent material, the potential of the source of the driving transistor is increased, whereby the voltage between a gate and the source (gate voltage) of the driving transistor is decreased. Accordingly, drain current of the driving transistor, that is, current supplied to the light-emitting element is decreased, resulting in a decrease in luminance of the light-emitting element.
In order to prevent the variation in luminance of the light-emitting elements due to the variation in the threshold voltages and the decrease in the luminance of the light-emitting elements due to deterioration of an electroluminescent layer, Patent Documents 1 and 2 each disclose a display device in which correction of the threshold voltage and correction of the potential of the anode are performed.